Hello,
I´m about to buy a digital SLR and I was for Nikon D40x, when a friend of mine told me how wonderful the sensor cleaner of his Canon Xti was (he thinks I´m wrong with the D40x because I might miss the focus motor built in the camera).
Anyway, I checked photo sites with personal reviews and found that many D40x owners have problems with the sensor getting dirty with dust easily. Is this truth? How often do yo have to clean it? Should I reconsider my choice regarding this feature in a Canon 400D?

I wouldn't choose a camera based on the sensor cleaning ability. Dust is an issue, but I don't think it's any worse with one camera than another. (unless we are talking about high end (pro) bodies with weather seals...but you still have to take the lens off to change it).

Cleaning the sensor isn't hard...and it mostly likely doens't have to be done all that often. I only cleaned mine once or twice in the first year.

Not having an AF motor...is a much bigger factor when choosing a camera. There is a debate going on, somewhere on the forum, about the D40 and why people should or shouldn't buy it, because of this issue.

Who cares about the dust cleaning garbage? I change my lenses all the time, and have not noticed any dust spots on my lens yet. I had a speck on the viewfinder somewhere, but it seemed to dislodge itself.

Anyways...dust removal is a bunch of crap. Especially on the XTi. Just get whatever you like better.

I will agree with the autofocus motor thingy though. Get a camera with a motor if you're goin Nikon.